Methods and systems for initial FCH processing

ABSTRACT

Methods and apparatus for initially decoding a frame control header (FCH) in an orthogonal frequency-division multiplexing (OFDM) or orthogonal frequency division multiple access (OFDMA) system in an effort to accurately determine the downlink frame prefix (DLFP) such that the remainder of an OFDM/A frame may be properly decoded are provided. Used, for example, when boosting factors applied in the transmitter to various elements of the OFDM/A frame and/or available pilots for the FCH are unknown, such methods may utilize a preamble channel estimate, the FCH pilots, or a combination thereof.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a divisional application of patent application Ser. No.12/123,406 entitled “Methods and Systems for Initial FCH Processing”filed May 19, 2008, which is hereby expressly incorporated by referenceherein.

TECHNICAL FIELD

Certain embodiments of the present disclosure generally relate towireless communication and, more particularly, to initially decoding aframe control header (FCH) in orthogonal frequency-division multiplexingand orthogonal frequency division multiple access (OFDM/A) systems.

BACKGROUND

OFDM and OFDMA wireless communication systems under IEEE 802.16 use anetwork of base stations to communicate with wireless devices (i.e.,mobile stations) registered for services in the systems based on theorthogonality of frequencies of multiple subcarriers and can beimplemented to achieve a number of technical advantages for widebandwireless communications, such as resistance to multipath fading andinterference. Each base station emits and receives radio frequency (RF)signals that convey data to and from the mobile stations. Such an RFsignal from a base station includes an overhead load, in addition to thedata load (voice and other data), for various communication managementfunctions. Each mobile station processes the information in the overheadload of each received signal prior to processing the data.

Under the current versions of the IEEE 802.16x standards for the OFDM/Asystems, every downlink subframe from a base station includes a preambleand a frame control header (FCH) following the preamble as part of theoverhead load. The preamble includes information for searching a celland a cell sector within a cell and for synchronizing a mobile stationin both time and frequency with the received downlink signal. The FCHportion of the downlink subframe includes 24 bits with information onthe downlink transmission format (e.g., the downlink media accessprotocol, or DL MAP) and control information for the downlink datareception (e.g., allocation of the subcarriers in the current downlinkframe).

Therefore, a receiver, such as a mobile station, first decodes the FCHto determine the position of the DL MAP, decodes the DL MAP of thecorresponding position, and then extracts the data. Due to the nature ofthe information in the FCH, if the reception of FCH fails or the FCH isdecoded incorrectly, the following downlink operations on the receiverside cannot be properly executed. Accordingly, proper interpretation ofthe FCH is important to OFDM and OFDMA system operation.

SUMMARY

Certain embodiments of the present disclosure generally relate toinitial decoding of a frame control header (FCH) in an orthogonalfrequency-division multiplexing (OFDM) system or orthogonal frequencydivision multiple access (OFDMA) system (e.g., OFDM/A systems) in aneffort to accurately determine the downlink frame prefix (DLFP).

Certain embodiments of the present disclosure provide a method. Themethod generally includes determining an initial channel estimate (CE)based on a preamble of a signal received via a wireless channel;generating an interpolated CE based on the initial CE by estimatingfrequency responses of the channel for other subcarriers not included inthe initial CE; extracting pilot and data subcarriers from an FCH of thesignal; from the interpolated CE, extracting channel estimatescorresponding to the extracted FCH pilot and data subcarriers; dividingthe extracted FCH pilot subcarriers by the extracted corresponding pilotchannel estimate and a normal boosting factor associated with the FCHpilot subcarriers to form equalized FCH pilot subcarriers; dividing theextracted FCH data subcarriers by the extracted corresponding datachannel estimate to form equalized FCH data subcarriers; determining anormalization factor corresponding to zone boosting based on theequalized FCH pilot subcarriers and the equalized FCH data subcarriers;normalizing the equalized FCH data subcarriers by dividing the equalizedFCH data subcarriers with the normalization factor; and determining theFCH based on the normalized FCH data subcarriers.

Certain embodiments of the present disclosure provide a receiver forwireless communication. The receiver generally includes initial channelestimation logic configured to determine an initial CE based on apreamble of a signal received by the receiver via a wireless channel;interpolation logic configured to generate an interpolated CE based onthe initial CE by estimating frequency responses of the channel forother subcarriers not included in the initial CE; subcarrier extractionlogic configured to extract pilot and data subcarriers from an FCH ofthe signal; channel estimation extraction logic configured to extract,from the interpolated CE, channel estimates corresponding to theextracted FCH pilot and data subcarriers; first division logicconfigured to divide the extracted FCH pilot subcarriers by theextracted corresponding pilot channel estimate and a normal boostingfactor associated with the FCH pilot subcarriers to form equalized FCHpilot subcarriers; second division logic configured to divide theextracted FCH data subcarriers by the extracted corresponding datachannel estimate to form equalized FCH data subcarriers; normalizationfactor determination logic configured to determine a normalizationfactor corresponding to zone boosting based on the equalized FCH pilotsubcarriers and the equalized FCH data subcarriers; third division logicconfigured to normalize the equalized FCH data subcarriers by dividingthe equalized FCH data subcarriers with the normalization factor; andinterpretation logic configured to determine the FCH based on thenormalized FCH data subcarriers.

Certain embodiments of the present disclosure provide an apparatus forwireless communication. The apparatus generally includes means fordetermining an initial CE based on a preamble of a signal received via awireless channel; means for generating an interpolated CE based on theinitial CE by estimating frequency responses of the channel for othersubcarriers not included in the initial CE; means for extracting pilotand data subcarriers from an FCH of the signal; means for extracting,from the interpolated CE, channel estimates corresponding to theextracted FCH pilot and data subcarriers; means for dividing theextracted FCH pilot subcarriers by the extracted corresponding pilotchannel estimate and a normal boosting factor associated with the FCHpilot subcarriers to form equalized FCH pilot subcarriers; means fordividing the extracted FCH data subcarriers by the extractedcorresponding data channel estimate to form equalized FCH datasubcarriers; means for determining a normalization factor correspondingto zone boosting based on the equalized FCH pilot subcarriers and theequalized FCH data subcarriers; means for normalizing the equalized FCHdata subcarriers by dividing the equalized FCH data subcarriers with thenormalization factor; and means for determining the FCH based on thenormalized FCH data sub carriers.

Certain embodiments of the present disclosure provide a mobile device.The mobile device generally includes a receiver front end for receivinga signal transmitted via a wireless channel; initial channel estimationlogic configured to determine an initial CE based on a preamble of thereceived signal; interpolation logic configured to generate aninterpolated CE based on the initial CE by estimating frequencyresponses of the channel for other subcarriers not included in theinitial CE; subcarrier extraction logic configured to extract pilot anddata subcarriers from an FCH of the signal; CE extraction logicconfigured to extract, from the interpolated CE, channel estimatescorresponding to the extracted FCH pilot and data subcarriers; firstdivision logic configured to divide the extracted FCH pilot subcarriersby the extracted corresponding pilot channel estimate and a normalboosting factor associated with the FCH pilot subcarriers to formequalized FCH pilot subcarriers; second division logic configured todivide the extracted FCH data subcarriers by the extracted correspondingdata channel estimate to form equalized FCH data subcarriers;normalization factor determination logic configured to determine anormalization factor corresponding to zone boosting based on theequalized FCH pilot subcarriers and the equalized FCH data subcarriers;third division logic configured to normalize the equalized FCH datasubcarriers by dividing the equalized FCH data subcarriers with thenormalization factor; and interpretation logic configured to determinethe FCH based on the normalized FCH data sub carriers.

Certain embodiments of the present disclosure provide acomputer-readable medium containing a program for initially decoding anFCH, which, when executed by a processor, performs certain operations.The operations generally include determining an initial CE based on apreamble of a signal received via a wireless channel; generating aninterpolated CE based on the initial CE by estimating frequencyresponses of the channel for other subcarriers not included in theinitial CE; extracting pilot and data subcarriers from the FCH of thesignal; from the interpolated CE, extracting channel estimatescorresponding to the extracted FCH pilot and data subcarriers; dividingthe extracted FCH pilot subcarriers by the extracted corresponding pilotchannel estimate and a normal boosting factor associated with the FCHpilot subcarriers to form equalized FCH pilot subcarriers; dividing theextracted FCH data subcarriers by the extracted corresponding datachannel estimate to form equalized FCH data subcarriers; determining anormalization factor corresponding to zone boosting based on theequalized FCH pilot subcarriers and the equalized FCH data subcarriers;normalizing the equalized FCH data subcarriers by dividing the equalizedFCH data subcarriers with the normalization factor; and determining theFCH based on the normalized FCH data sub carriers.

Certain embodiments of the present disclosure provide a method. Themethod generally includes extracting pilot and data subcarriers from anFCH of a signal received via a wireless channel; determining an initialCE based on the extracted FCH pilot subcarriers; generating aninterpolated CE based on the initial CE by estimating frequencyresponses of the channel for the extracted FCH data subcarriers; fromthe interpolated CE, extracting a channel estimate corresponding to theFCH data subcarriers; dividing the extracted FCH data subcarriers by theextracted channel estimate to form equalized FCH data subcarriers; anddetermining the FCH based on the equalized FCH data subcarriers.

Certain embodiments of the present disclosure provide acomputer-readable medium containing a program for initially decoding anFCH, which, when executed by a processor, performs certain operations.The operation generally include extracting pilot and data subcarriersfrom the FCH of a signal received via a wireless channel; determining aninitial CE based on the extracted FCH pilot subcarriers; generating aninterpolated CE based on the initial CE by estimating frequencyresponses of the channel for the extracted FCH data subcarriers; fromthe interpolated CE, extracting a channel estimate corresponding to theFCH data subcarriers; dividing the extracted FCH data subcarriers by theextracted channel estimate to form equalized FCH data subcarriers; anddetermining the FCH based on the equalized FCH data subcarriers.

Certain embodiments of the present disclosure provide an apparatus forwireless communication. The apparatus generally includes means forextracting pilot and data subcarriers from an FCH of a signal receivedvia a wireless channel; means for determining an initial CE based on theextracted FCH pilot subcarriers; means for generating an interpolated CEbased on the initial CE by estimating frequency responses of the channelfor the extracted FCH data subcarriers; means for extracting, from theinterpolated CE, a channel estimate corresponding to the FCH datasubcarriers; means for dividing the extracted FCH data subcarriers bythe extracted channel estimate to form equalized FCH data subcarriers;and means for determining the FCH based on the equalized FCH datasubcarriers.

Certain embodiments of the present disclosure provide a receiver forwireless communication. The receiver generally includes subcarrierextraction logic configured to extract pilot and data subcarriers froman FCH of a signal received via a wireless channel; initial channelestimation logic configured to determine an initial CE based on theextracted FCH pilot subcarriers; interpolation logic configured togenerate an interpolated CE based on the initial CE by estimatingfrequency responses of the channel for the extracted FCH datasubcarriers; CE extraction logic configured to extract, from theinterpolated CE, a channel estimate corresponding to the FCH datasubcarriers; division logic configured to divide the extracted FCH datasubcarriers by the extracted channel estimate to form equalized FCH datasubcarriers; and interpretation logic configured to determine the FCHbased on the equalized FCH data sub carriers.

Certain embodiments of the present disclosure provide a mobile device.The mobile device generally includes a receiver front end for receivinga signal transmitted via a wireless channel; subcarrier extraction logicconfigured to extract pilot and data subcarriers from an FCH of thereceived signal; initial channel estimation logic configured todetermine an initial CE based on the extracted FCH pilot subcarriers;interpolation logic configured to generate an interpolated CE based onthe initial CE by estimating frequency responses of the channel for theextracted FCH data subcarriers; CE extraction logic configured toextract, from the interpolated CE, a channel estimate corresponding tothe FCH data subcarriers; division logic configured to divide theextracted FCH data subcarriers by the extracted channel estimate to formequalized FCH data subcarriers; and interpretation logic configured todetermine the FCH based on the equalized FCH data subcarriers.

Certain embodiments of the present disclosure provide a method. Themethod generally includes determining a first initial CE based on apreamble of a signal received via a wireless channel; generating a firstinterpolated CE by estimating frequency responses of the channel forsubcarriers not included in the first initial CE; extracting pilot anddata subcarriers from an FCH of the signal; from the first interpolatedCE, extracting a channel estimate corresponding to the FCH pilotsubcarriers; determining a second initial CE based on the extracted FCHpilot subcarriers; estimating a zone boosting factor for the signal;normalizing the second initial CE by the estimated zone boosting factor;generating a second interpolated CE based on the extracted correspondingpilot channel estimate and the normalized second initial CE byestimating frequency responses of the channel for subcarriers notincluded in the pilot channel estimate or the normalized second initialCE; from the second interpolated CE, extracting a channel estimatecorresponding to the extracted FCH data subcarriers; dividing theextracted FCH data subcarriers by the extracted corresponding datachannel estimate and the estimated zone boosting factor to formequalized FCH data subcarriers; and determining the FCH based on theequalized FCH data subcarriers.

Certain embodiments of the present disclosure provide acomputer-readable medium containing a program for initially decoding anFCH, which, when executed by a processor, performs certain operations.The operations generally include determining a first initial CE based ona preamble of a signal received via a wireless channel; generating afirst interpolated CE by estimating frequency responses of the channelfor subcarriers not included in the first initial CE; extracting pilotand data subcarriers from the FCH of the signal; from the firstinterpolated CE, extracting a channel estimate corresponding to the FCHpilot subcarriers; determining a second initial CE based on theextracted FCH pilot subcarriers; estimating a zone boosting factor forthe signal; normalizing the second initial CE by the estimated zoneboosting factor; generating a second interpolated CE based on theextracted corresponding pilot channel estimate and the normalized secondinitial CE by estimating frequency responses of the channel forsubcarriers not included in the pilot channel estimate or the normalizedsecond initial CE; from the second interpolated CE, extracting a channelestimate corresponding to the extracted FCH data subcarriers; dividingthe extracted FCH data subcarriers by the extracted corresponding datachannel estimate and the estimated zone boosting factor to formequalized FCH data subcarriers; and determining the FCH based on theequalized FCH data subcarriers.

Certain embodiments of the present disclosure provide an apparatus forwireless communication. The apparatus generally includes means fordetermining a first initial CE based on a preamble of a signal receivedvia a wireless channel; means for generating a first interpolated CE byestimating frequency responses of the channel for subcarriers notincluded in the first initial CE; means for extracting pilot and datasubcarriers from an FCH of the signal; means for extracting, from thefirst interpolated CE, a channel estimate corresponding to the FCH pilotsubcarriers; means for determining a second initial CE based on theextracted FCH pilot subcarriers; means for estimating a zone boostingfactor for the signal; normalizing the second initial CE by theestimated zone boosting factor; means for generating a secondinterpolated CE based on the extracted corresponding pilot channelestimate and the normalized second initial CE by estimating frequencyresponses of the channel for subcarriers not included in the pilotchannel estimate or the normalized second initial CE; means forextracting, from the second interpolated CE, a channel estimatecorresponding to the extracted FCH data subcarriers; means for dividingthe extracted FCH data subcarriers by the extracted corresponding datachannel estimate and the estimated zone boosting factor to formequalized FCH data subcarriers; and means for determining the FCH basedon the equalized FCH data subcarriers.

Certain embodiments of the present disclosure provide a receiver forwireless communication. The receiver generally includes first initialchannel estimation logic configured to determine a first initial CEbased on a preamble of a signal received via a wireless channel; firstinterpolation logic configured to generate a first interpolated CE byestimating frequency responses of the channel for subcarriers notincluded in the first initial CE; subcarrier extraction logic configuredto extract pilot and data subcarriers from an FCH of the signal; firstCE extraction logic configured to extract, from the first interpolatedCE, a channel estimate corresponding to the FCH pilot subcarriers;second initial channel estimation logic configured to determine a secondinitial CE based on the extracted FCH pilot subcarriers; zone boostingfactor estimation logic configured to estimate a zone boosting factorfor the signal; normalization logic configured to normalize the secondinitial CE by the estimated zone boosting factor; second interpolationlogic configured to generate a second interpolated CE based on theextracted corresponding pilot channel estimate and the normalized secondinitial CE by estimating frequency responses of the channel forsubcarriers not included in the pilot channel estimate or the normalizedsecond initial CE; second CE extraction logic configured to extract,from the second interpolated CE, a channel estimate corresponding to theextracted FCH data subcarriers; division logic configured to divide theextracted FCH data subcarriers by the extracted corresponding datachannel estimate and the estimated zone boosting factor to formequalized FCH data subcarriers; and interpretation logic configured todetermine the FCH based on the equalized FCH data sub carriers.

Certain embodiments of the present disclosure provide a mobile device.The mobile device generally includes a receiver front end for receivinga signal transmitted via a wireless channel; first initial channelestimation logic configured to determine a first initial CE based on apreamble of the received signal; first interpolation logic configured togenerate a first interpolated CE by estimating frequency responses ofthe channel for subcarriers not included in the first initial CE;subcarrier extraction logic configured to extract pilot and datasubcarriers from an FCH of the signal; first CE extraction logicconfigured to extract, from the first interpolated CE, a channelestimate corresponding to the FCH pilot subcarriers; second initialchannel estimation logic configured to determine a second initial CEbased on the extracted FCH pilot subcarriers; zone boosting factorestimation logic configured to estimate a zone boosting factor for thesignal; normalization logic configured to normalize the second initialCE by the estimated zone boosting factor; second interpolation logicconfigured to generate a second interpolated CE based on the extractedcorresponding pilot channel estimate and the normalized second initialCE by estimating frequency responses of the channel for subcarriers notincluded in the pilot channel estimate or the normalized second initialCE; second CE extraction logic configured to extract, from the secondinterpolated CE, a channel estimate corresponding to the extracted FCHdata subcarriers; division logic configured to divide the extracted FCHdata subcarriers by the extracted corresponding data channel estimateand the estimated zone boosting factor to form equalized FCH datasubcarriers; and interpretation logic configured to determine the FCHbased on the equalized FCH data subcarriers.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentdisclosure can be understood in detail, a more particular description,briefly summarized above, may be had by reference to embodiments, someof which are illustrated in the appended drawings. It is to be noted,however, that the appended drawings illustrate only certain typicalembodiments of this disclosure and are therefore not to be consideredlimiting of its scope, for the description may admit to other equallyeffective embodiments.

FIG. 1 illustrates an example wireless communication system, inaccordance with certain embodiments of the present disclosure.

FIG. 2 illustrates various components that may be utilized in a wirelessdevice in accordance with certain embodiments of the present disclosure.

FIG. 3 illustrates an example transmitter and an example receiver thatmay be used within a wireless communication system that utilizesorthogonal frequency-division multiplexing and orthogonal frequencydivision multiple access (OFDM/OFDMA) technology in accordance withcertain embodiments of the present disclosure.

FIGS. 4A and 4B illustrate an example OFDM/A frame for Time DivisionDuplex (TDD) and the format of the Frame Control Header (FCH) containedtherein, the FCH including downlink Frame Prefix (DLFP) information, inaccordance with certain embodiments of the present disclosure.

FIG. 5 illustrates transmission and reception across a wireless channelwith normal, zone, and subchannel boosting, in accordance with certainembodiments of the present disclosure.

FIG. 6 is a conceptual block diagram of initial FCH/DLFP decodingfollowed by normal decoding, in accordance with certain embodiments ofthe present disclosure.

FIG. 7 illustrates initial FCH/DLFP decoding based on channel estimation(CE) using the preamble of an OFDM/A frame, in accordance with certainembodiments of the present disclosure.

FIG. 8 illustrates initial FCH/DLFP decoding based on FCH pilots of anOFDM/A frame, in accordance with certain embodiments of the presentdisclosure.

FIG. 9 illustrates initial FCH/DLFP decoding based on FCH pilots and onCE using the preamble of an OFDM/A frame, in accordance with certainembodiments of the present disclosure.

FIG. 10 is a flow chart of example operations for initial FCH/DLFPdecoding based on CE using the preamble of an OFDM/A frame, inaccordance with certain embodiments of the present disclosure.

FIG. 10A is a block diagram of means corresponding to the exampleoperations for initial FCH/DLFP decoding of FIG. 10, in accordance withcertain embodiments of the present disclosure.

FIG. 11 is a flow chart of example operations for initial FCH/DLFPdecoding based on FCH pilots of an OFDM/A frame, in accordance withcertain embodiments of the present disclosure.

FIG. 11A is a block diagram of means corresponding to the exampleoperations for initial FCH/DLFP decoding of FIG. 11, in accordance withcertain embodiments of the present disclosure.

FIG. 12 is a flow chart of example operations for initial FCH/DLFPdecoding based on FCH pilots and on CE using the preamble of an OFDM/Aframe, in accordance with certain embodiments of the present disclosure.

FIG. 12A is a block diagram of means corresponding to the exampleoperations for initial FCH/DLFP decoding of FIG. 12, in accordance withcertain embodiments of the present disclosure.

DETAILED DESCRIPTION

Certain embodiments of the present disclosure provide techniques andapparatus for initially decoding a frame control header (FCH) in anorthogonal frequency-division multiplexing (OFDM) or orthogonalfrequency division multiple access (OFDMA) system in an effort toaccurately determine the downlink frame prefix (DLFP) such that theremainder of an OFDM/A frame may be properly decoded. Used, for example,when boosting factors applied in the transmitter to various elements ofthe OFDM/A frame and/or available pilots for the FCH are unknown, thesetechniques may utilize a preamble channel estimate, the FCH pilots, or acombination thereof

Exemplary Wireless Communication System

The methods and apparatus of the present disclosure may be utilized in abroadband wireless communication system. The term “broadband wireless”refers to technology that provides wireless, voice, Internet, and/ordata network access over a given area.

WiMAX, which stands for the Worldwide Interoperability for MicrowaveAccess, is a standards-based broadband wireless technology that provideshigh-throughput broadband connections over long distances. There are twomain applications of WiMAX today: fixed WiMAX and mobile WiMAX. FixedWiMAX applications are point-to-multipoint, enabling broadband access tohomes and businesses, for example. Mobile WiMAX offers the full mobilityof cellular networks at broadband speeds.

Mobile WiMAX is based on OFDM (orthogonal frequency-divisionmultiplexing) and OFDMA (orthogonal frequency division multiple access)technology. OFDM is a digital multi-carrier modulation technique thathas recently found wide adoption in a variety of high-data-ratecommunication systems. With OFDM, a transmit bit stream is divided intomultiple lower-rate substreams. Each substream is modulated with one ofmultiple orthogonal subcarriers and sent over one of a plurality ofparallel subchannels. OFDMA is a multiple access technique in whichusers are assigned subcarriers in different time slots. OFDMA is aflexible multiple-access technique that can accommodate many users withwidely varying applications, data rates, and quality of servicerequirements.

The rapid growth in wireless internets and communications has led to anincreasing demand for high data rate in the field of wirelesscommunications services. OFDM/OFDMA systems are today regarded as one ofthe most promising research areas and as a key technology for the nextgeneration of wireless communications. This is due to the fact thatOFDM/OFDMA modulation schemes can provide many advantages such asmodulation efficiency, spectrum efficiency, flexibility, and strongmultipath immunity over conventional single carrier modulation schemes.

IEEE 802.16x is an emerging standard organization to define an airinterface for fixed and mobile broadband wireless access (BWA) systems.Those standards at least define four different physical layers (PHYs)and one media access control (MAC) layer. The OFDM and OFDMA physicallayer of the four physical layers are generally considered the mostpopular in the fixed and mobile BWA areas respectively.

FIG. 1 illustrates an example of a wireless communication system 100.The wireless communication system 100 may be a broadband wirelesscommunication system. The wireless communication system 100 may providecommunication for a number of cells 102, each of which is serviced by abase station 104. A base station 104 may be a fixed station thatcommunicates with user terminals 106. The base station 104 mayalternatively be referred to as an access point, a Node B, or some otherterminology.

FIG. 1 depicts various user terminals 106 dispersed throughout thesystem 100. The user terminals 106 may be fixed (i.e., stationary) ormobile. The user terminals 106 may alternatively be referred to asremote stations, access terminals, terminals, subscriber units, mobilestations, stations, user equipment, etc. The user terminals 106 may bewireless devices, such as cellular phones, personal digital assistants(PDAs), handheld devices, wireless modems, laptop computers, personalcomputers, etc.

A variety of algorithms and methods may be used for transmissions in thewireless communication system 100 between the base stations 104 and theuser terminals 106. For example, signals may be sent and receivedbetween the base stations 104 and the user terminals 106 in accordancewith OFDM/OFDMA techniques. If this is the case, the wirelesscommunication system 100 may be referred to as an OFDM/OFDMA system.

A communication link that facilitates transmission from a base station104 to a user terminal 106 may be referred to as a downlink 108, and acommunication link that facilitates transmission from a user terminal106 to a base station 104 may be referred to as an uplink 110.Alternatively, a downlink 108 may be referred to as a forward link or aforward channel, and an uplink 110 may be referred to as a reverse linkor a reverse channel.

A cell 102 may be divided into multiple sectors 112. A sector 112 is aphysical coverage area within a cell 102. Base stations 104 within awireless communication system 100 may utilize antennas that concentratethe flow of power within a particular sector 112 of the cell 102. Suchantennas may be referred to as directional antennas.

FIG. 2 illustrates various components that may be utilized in a wirelessdevice 202. The wireless device 202 is an example of a device that maybe configured to implement the various methods described herein. Thewireless device 202 may be a base station 104 or a user terminal 106.

The wireless device 202 may include a processor 204 which controlsoperation of the wireless device 202. The processor 204 may also bereferred to as a central processing unit (CPU). Memory 206, which mayinclude both read-only memory (ROM) and random access memory (RAM),provides instructions and data to the processor 204. A portion of thememory 206 may also include non-volatile random access memory (NVRAM).The processor 204 typically performs logical and arithmetic operationsbased on program instructions stored within the memory 206. Theinstructions in the memory 206 may be executable to implement themethods described herein.

The wireless device 202 may also include a housing 208 that may includea transmitter 210 and a receiver 212 to allow transmission and receptionof data between the wireless device 202 and a remote location. Thetransmitter 210 and receiver 212 may be combined into a transceiver 214.An antenna 216 may be attached to the housing 208 and electricallycoupled to the transceiver 214. The wireless device 202 may also include(not shown) multiple transmitters, multiple receivers, multipletransceivers, and/or multiple antennas.

The wireless device 202 may also include a signal detector 218 that maybe used in an effort to detect and quantify the level of signalsreceived by the transceiver 214. The signal detector 218 may detect suchsignals as total energy, pilot energy per pseudonoise (PN) chips, powerspectral density, and other signals. The wireless device 202 may alsoinclude a digital signal processor (DSP) 220 for use in processingsignals.

The various components of the wireless device 202 may be coupledtogether by a bus system 222, which may include a power bus, a controlsignal bus, and a status signal bus in addition to a data bus.

FIG. 3 illustrates an example of a transmitter 302 that may be usedwithin a wireless communication system 100 that utilizes OFDM/OFDMA.Portions of the transmitter 302 may be implemented in the transmitter210 of a wireless device 202. The transmitter 302 may be implemented ina base station 104 for transmitting data 306 to a user terminal 106 on adownlink 108. The transmitter 302 may also be implemented in a userterminal 106 for transmitting data 306 to a base station 104 on anuplink 110.

Data 306 to be transmitted is shown being provided as input to aserial-to-parallel (S/P) converter 308. The S/P converter 308 may splitthe transmission data into N parallel data streams 310.

The N parallel data streams 310 may then be provided as input to amapper 312. The mapper 312 may map the N parallel data streams 310 ontoN constellation points. The mapping may be done using some modulationconstellation, such as binary phase-shift keying (BPSK), quadraturephase-shift keying (QPSK), 8 phase-shift keying (8PSK), quadratureamplitude modulation (QAM), etc. Thus, the mapper 312 may output Nparallel symbol streams 316, each symbol stream 316 corresponding to oneof the N orthogonal subcarriers of the inverse fast Fourier transform(IFFT) 320. These N parallel symbol streams 316 are represented in thefrequency domain and may be converted into N parallel time domain samplestreams 318 by an IFFT component 320.

A brief note about terminology will now be provided. N parallelmodulations in the frequency domain are equal to N modulation symbols inthe frequency domain, which are equal to N mapping and N-point IFFT inthe frequency domain, which is equal to one (useful) OFDM symbol in thetime domain, which is equal to N samples in the time domain. One OFDMsymbol in the time domain, N_(s), is equal to N_(cp) (the number ofguard samples per OFDM symbol)+N (the number of useful samples per OFDMsymbol).

The N parallel time domain sample streams 318 may be converted into anOFDM/OFDMA symbol stream 322 by a parallel-to-serial (P/S) converter324. A guard insertion component 326 may insert a guard interval betweensuccessive OFDM/OFDMA symbols in the OFDM/OFDMA symbol stream 322. Theoutput of the guard insertion component 326 may then be upconverted to adesired transmit frequency band by a radio frequency (RF) front end 328.An antenna 330 may then transmit the resulting signal 332.

FIG. 3 also illustrates an example of a receiver 304 that may be usedwithin a wireless communication system 100 that utilizes OFDM/OFDMA.Portions of the receiver 304 may be implemented in the receiver 212 of awireless device 202. The receiver 304 may be implemented in a userterminal 106 for receiving data 306 from a base station 104 on adownlink 108. The receiver 304 may also be implemented in a base station104 for receiving data 306 from a user terminal 106 on an uplink 110.

The transmitted signal 332 is shown traveling over a wireless channel334. When a signal 332′ is received by an antenna 330′, the receivedsignal 332′ may be downconverted to a baseband signal by an RF front end328′. A guard removal component 326′ may then remove the guard intervalthat was inserted between OFDM/OFDMA symbols by the guard insertioncomponent 326.

The output of the guard removal component 326′ may be provided to an S/Pconverter 324′. The S/P converter 324′ may divide the OFDM/OFDMA symbolstream 322′ into the N parallel time-domain symbol streams 318′, each ofwhich corresponds to one of the N orthogonal subcarriers. A fast Fouriertransform (FFT) component 320′ may convert the N parallel time-domainsymbol streams 318′ into the frequency domain and output N parallelfrequency-domain symbol streams 316′.

A demapper 312′ may perform the inverse of the symbol mapping operationthat was performed by the mapper 312, thereby outputting N parallel datastreams 310′. A P/S converter 308′ may combine the N parallel datastreams 310′ into a single data stream 306′. Ideally, this data stream306′ corresponds to the data 306 that was provided as input to thetransmitter 302.

Exemplary OFDM/A Frame

Referring now to FIG. 4A, an OFDM/A frame 400 for a Time Division Duplex(TDD) implementation is depicted as a typical, but not limiting,example. Other implementations of an OFDM/A frame, such as Full andHalf-Duplex Frequency Division Duplex (FDD) may be used, in which casethe frame is the same except that both downlink (DL) and uplink (UL) aretransmitted simultaneously over different carriers. In the TDDimplementation, each frame may be divided into a DL subframe 402 and aUL subframe 404, which may be separated by a small guard interval406—or, more specifically, by Transmit/Receive and Receive/TransmitTransition Gaps (TTG and RTG, respectively)—in an effort to prevent DLand UL transmission collisions. The DL-to-UL-subframe ratio may bevaried from 3:1 to 1:1 to support different traffic profiles.

Within the OFDM/A frame 400, various control information may beincluded. For example, the first OFDM/A symbol of the frame 400 may be apreamble 408, which may contain several pilot signals (pilots) used forsynchronization. Fixed pilot sequences inside the preamble 408 may allowthe receiver 304 to estimate frequency and phase errors and tosynchronize to the transmitter 302. Moreover, fixed pilot sequences inthe preamble 408 may be utilized to estimate and equalize wirelesschannels. The preamble 408 may contain BPSK-modulated carriers and istypically one OFDM symbol long. The carriers of the preamble 408 may bepower boosted and are typically a few decibels (dB) (e.g., 9 dB) higherthan the power level in the frequency domain of data portions in theWiMAX signal. The number of preamble carriers used may indicate which ofthe three segments of the zone are used. For example, carriers 0, 3, 6,. . . may indicate that segment 0 is to be used, carriers 1, 4, 7, . . .may indicate that segment 1 is to be used, and carriers 2, 5, 8, . . .may indicate that segment 3 is to be used.

A Frame Control Header (FCH) 410 may follow the preamble 408. The FCH410 may provide frame configuration information, such as the usablesubchannels, the modulation and coding scheme, and the Media AccessProtocol (MAP) message length for the current OFDM/A frame. A datastructure, such as the downlink Frame Prefix (DLFP) 412, outlining theframe configuration information may be mapped to the FCH 410. For MobileWiMAX, the DLFP 412 may comprise six bits for the used subchannel (SCH)bitmap 412 a, a reserved bit 412 b set to 0, two bits for the repetitioncoding indication 412 c, three bits for the coding indication 412 d,eight bits for the Media Access Protocol (MAP) message length 412 e, andfour reserved bits 412 f set to 0 for a total of 24 bits in the DLFP 412as illustrated in FIG. 4B. Before being mapped to the FCH 410, the24-bit DLFP may be duplicated to form a 48-bit block, which is theminimal forward error correction (FEC) block size.

Following the FCH 410, a DL MAP 414 and a UL MAP 416 may specifysubchannel allocation and other control information for the DL and ULsubframes 402, 404. In the case of OFDMA, multiple users may beallocated data regions within the frame, and these allocations may bespecified in the DL and UL MAP messages 414, 416. The MAP messages mayinclude the burst profile for each user, which defines the modulationand coding scheme used in a particular link. The DL subframe 402 of theOFDM/A frame may include DL bursts of various bit lengths containing thedownlink data being communicated. Thus, the DL MAP 414 may describe thelocation of the bursts contained in the downlink zones and the number ofdownlink bursts, as well as their offsets and lengths in both the time(i.e., symbol) and the frequency (i.e., subchannel) directions.

Likewise, the UL subframe 404 may include UL bursts of various bitlengths composed of the uplink data being communicated. Therefore, theUL MAP 416, transmitted as the first burst in the downlink subframe 402,may contain information about the location of the UL burst for differentusers. The UL subframe 404 may include additional control information asillustrated in FIG. 4A. The UL subframe 404 may include a UL ACK 418allocated for the mobile station (MS) to feed back a DL hybrid automaticrepeat request acknowledge (HARQ ACK) and/or a UL CQICH 420 allocatedfor the MS to feed back channel state information on the Channel QualityIndicator channel (CQICH). Furthermore, the UL subframe 404 may comprisea UL Ranging subchannel 422. The UL Ranging subchannel 422 may beallocated for the MS to perform closed-loop time, frequency, and poweradjustment, as well as bandwidth requests.

Altogether, the preamble 408, the FCH 410, the DL MAP 414, and the ULMAP 416 may carry information that enables the receiver 304 to correctlydemodulate the received signal.

For OFDMA, different “modes” can be used for transmission in DL and UL.An area in the time domain where a certain mode is used is generallyreferred to as a zone. One type of zone is called DL-PUSC (downlinkpartial usage of subchannels) and does not use all the subchannelsavailable to it (i.e., a DL-PUSC zone only uses particular groups ofsubchannels). There may be a total of six subchannel groups, which canbe assigned to up to three segments. Thus, a segment can contain one tosix subchannels (e.g., segment 0 contains three subchannel groups,segment 1 contains two, and segment 2 contains one subchannel group).Another type of zone is called DL-FUSC (downlink full usage ofsubchannels). Unlike DL-PUSC, DL-FUSC does not use any segments, but candistribute all bursts over the complete frequency range.

Exemplary OFDM/A Transmission and Reception

Before an OFDM/A frame, such as the example OFDM/A frame 400 of FIG. 4A,is transmitted by the transmitter 302, various subcarriers of theprocessed and mapped OFDM/A frame exiting the mapper 312 may be boostedin the frequency domain according to corresponding boosting factors asillustrated in FIG. 5. Since all constellations (e.g., BPSK, QPSK,16QAM, and 64QAM) in the diagram are normalized to achieve equal averagepower, the subcarriers may be boosted with different boosting factorsaccording to their subcarrier index k. A normal boosting factor (B_(n))may be applied to differentiate between subcarriers in the preamble,pilot subcarriers, and data subcarriers. Conceptually, the mapped signal(X_(m)) exiting the mapper 312 may be multiplied with B_(n) in a firstmultiplier 502 to produce a mapped and normal boosted signal (X_(mn)).For data subcarriers, the normal boosting factor is typically equal to 1(B_(n) _(—) _(dscr)=1), indicating that data subcarriers may notnormally be boosted. Unlike the data subcarriers, the preamble and thepilot subcarriers may have normal boosting factors greater than 1 (B_(n)_(—) _(pascr), B_(n) _(—) _(pscr)>1). For example, the power of thesubcarriers in the downlink preamble may be boosted by about 9 dB, andthe power of the pilot subcarriers may be boosted by approximately 2.5dB when compared to the power of the data subcarriers. The normalboosting factor may be fixed.

When not all subchannels are used within the first DL-PUSC zone, zoneboosting may be applied, thereby boosting the pilot and data subcarriersin the corresponding zone. The subcarrier power of the zone may beincreased as follows:10 log(N _(useful) /N _(allowed))where Nuseful is the number of all useful subcarriers (of all thesubchannels) depending on the permutation scheme and excluding the DCsubcarrier, and Nallowed is the number of subcarriers of the selectedsubchannels (that are allowed to be used in the zone). Conceptually, themapped and normal boosted signal (Xmn) may be multiplied with a zoneboosting factor (Bz) in a second multiplier 504 to generate a mapped,normal boosted, and zone boosted signal (Xmnz) as illustrated in FIG. 5.For pilot and data subcarriers in the DL-PUSC, the zone boosting factormay be greater than 1 (Bz_pusc>1), whereas the zone boosting factor forthe preamble and the other downlink zones may be equal to 1(Bz_pa=Bz_fusc=Bz_amc=1). The zone boosting factor (Bz) may be writtento (and later extracted from) the used subchannel bitmap 412 a in theDLFP, which is mapped to the FCH 410.

For some embodiments, data subcarriers within certain subchannels mayhave a subchannel (SCH) boosting factor (B_(s)) applied according to theDL MAP 414. Conceptually, the mapped, normal boosted, and zone boostedsignal (X_(mnz)) may be multiplied with the SCH boosting factor (B_(s))in a third multiplier 506 to generate a mapped, normal boosted, zoneboosted, and SCH boosted signal (X_(mnzs)) as illustrated in FIG. 5. Forsuch data subcarriers, the SCH boosting factor may be greater than 1(B_(s) _(—) _(dscr)>1), whereas the SCH boosting factor for the preambleand the pilot subcarriers may be equal to 1 (B_(s) _(—) _(pa)=B_(s) _(—)_(pscr)=1).

Once the boosting factors have been applied to the various subcarriersin the frequency domain, the resulting signal X_(mnzs) may be convertedto the time domain by the IFFT component 320 as described above. Thetransmitter 302 may transmit the time domain signal across a wirelesschannel h 334 having a transfer function H to be received by thereceiver 304.

The FFT component 320′ of the receiver 304 may convert the receivedsignal into the frequency domain to be processed and decoded in laterstages, the result of the FFT being the signal Y_(mnzs)=HX_(mnzs).Therefore, for the preamble signal in the frequency domain, thetransmitted preamble (X_(pa)) and the received preamble (Y_(pa)) may beexpressed as follows:X _(pa) =X _(mnzs) =X _(m) B _(n) _(—) _(pascr)Y _(pa) =Y _(mnzs) =HX _(mnzs) =HX _(m) B _(n) _(—) _(pascr)since there is no zone boosting or SCH boosting for the preamble (i.e.,B_(z) _(—) _(pa)=B_(s) _(—) _(pa)=1). For pilot signals of the FCH(containing the DLFP) in the frequency domain, the transmitted FCH/DLFPpilots (X_(fchp)) and the received FCH/DLFP pilots (Y_(fchp)) may beexpressed as follows:X _(fchp) =X _(mnzs) =X _(m) B _(n) _(—) _(pscr) B _(z)Y _(fchp) =Y _(mnzs) =HX _(mnzs) =HX _(m) B _(n) _(—) _(pscr) B _(z)since there is no SCH boosting for the FCH pilots (i.e., B_(s) _(—)_(pscr)=1). For FCH/DLFP data signals in the frequency domain, thetransmitted FCH/DLFP data (X_(fchd)) and the received FCH/DLFP data(Y_(fchd)) may be expressed as follows:X _(fchd) =X _(mnzs) =X _(m) B _(z)Y _(fchd) =Y _(mnzs) =HX _(mnzs) =HX _(m) B _(z)since there is no normal boosting or SCH boosting for the FCH data(i.e., B_(n) _(—) _(dscr)=B_(s) _(—) _(dscr)=1).

The Y_(mnzs) signal output from the FFT component 320′ may be sent todata subcarrier extraction logic 508, the data subcarriers correspondingto the available pilot subcarriers. The output of the FFT component 320′may also be sent to available pilot subcarrier extraction logic 510, andchannel estimation (CE) logic 512 may estimate the channel based on theextracted pilot subcarriers. The output of the CE logic 512 may be aFourier transform of the channel h. Equalization (EQ) of the datasubcarriers based on the estimated channel from the CE logic 512 may beperformed in the EQ combiner 514, and channel state information (CSI),also based on the estimated channel, may be arranged in the CSI block516.

In a log likelihood ratio (LLR) block 518, the outputs of the EQcombiner 514 and the CSI block 516 may be processed to form an outputweighted signal according to LLR calculations, for example. For someembodiments, the processing may include multiplying a demodulatedreceived signal and the corresponding CSI signal from the CSI block 516.The output weighted signal may be sent from the LLR block 518 to thechannel decoder 520, which may decode the demapped bits and output aninterpreted message.

Exemplary Overall Decoding Scheme

Referring now to FIG. 6, a conceptual block diagram 600 of initialFCH/DLFP decoding followed by normal decoding is illustrated. Inpractice, many of the blocks contained therein may be combined with theprocesses occurring in parallel, but the block diagram 600 of FIG. 6depicts a possible processing sequence when receiving a transmittedOFDM/A frame to understand the complexities of properly decoding the FCH410.

As described above, the received signal may be processed in the FFTcomponent 320′ such that the signal is converted into the frequencydomain for processing of the subcarriers. The Y_(mnzs) signal outputfrom the FFT component 320′ may enter an FCH decoder 602 in an effort toextract the DLFP from the FCH 410 to discern the used SCH bitmap,extract the available pilots and the zone boosting factor (B_(z)), andbe able to read the DL MAP 414. For initial FCH/DLFP decoding, theproblem is that the used SCH bitmap 412 a, the zone boosting factor, andthe available pilots may most likely be unknown, especially in the caseof a cold start where OFDM/A frames have not already been transmitted.Therefore, it is difficult to apply a normal CE/EQ scheme at this stage.If OFDM/A frames have already been transmitted, then the used SCH bitmap412 a may be extracted using the FCH/DLFP decoded in a previous frame.However, the subchannel bitmaps may change from frame to frame, so thereis no guarantee that the used SCH bitmap from a previous frame willapply to the current frame. To circumvent this problem in the FCHdecoder 602, the Y_(mnzs) signal may be sent to a special EQ combiner603 and special channel estimation (CE) logic 604 for FCH decoding.

The outputs of the EQ combiner 603 and the CE logic 604 for FCH decodingmay be sent to the LLR block 518 and the CSI block 516, such that theoutput of the LLR block 518 may be decoded by the channel decoder 520 asdescribed above. Once, the FCH 410 has been decoded, the DLFP 412 mappedto the FCH can be interpreted. For example, the used SCH bitmap 412 amay be extracted in bitmap extraction logic 606, from which theavailable pilots (P_(available)) and the zone boosting factor (B_(e))may be determined in the P_(available) and B_(z) extraction logic 608.

In the normal decoder 610, normal channel estimation and equalizationmay be performed on the output of the FFT component 320′ as describedabove, using the extracted P_(available) and B_(z). Channel estimationmay be performed based on an initial CE with a two-dimensional (2-D)time-frequency interpolation scheme that utilizes CE of the preamble andall available pilots of multiple symbols including all the FCH pilots.For some embodiments, the FCH 410 may be decoded again for more accurateFCH decoding after the available pilots and the zone boosting factorhave been extracted, and the new DLFP 412′ may be compared to theinitially decoded and interpreted DLFP 412 in DLFP confirmation logic612. However, the process of comparing the initially interpreted DLFP412 and the new DLFP 412′ may be omitted if the initial FCH decodingscheme is sufficiently reliable.

After the signal has been decoded in the channel decoder 520 asdescribed above, the DL MAP 414 may be extracted now that the codingindication 412 d and the MAP message length 412 e have been interpretedfrom the DLFP. SCH boosting factor extraction logic 616 may be used toextract B_(s) for each data burst from the DL MAP 414. The SCH boostingfactor may be used by the EQ combiner 514 in an effort to decode thedata bursts but need not be used by the CE logic 512 since there is mostlikely no SCH boosting for the pilot subcarriers in the data bursts 614(B_(s) _(—) _(pscr)=1). Furthermore, SCH boosting is not typicallyapplied to the FCH 410 or the DL MAP 414, so the EQ combiner 514 neednot know B_(s) in order to decode these messages.

Exemplary Initial FCH Decoding using the Preamble

FIG. 7 illustrates a block diagram 700 for one method of initialFCH/DLFP decoding based on initial channel estimation (CE) using thepreamble 408 of an OFDM/A frame directly. Assuming that the wirelesschannel h is static for three OFDM symbols, this initial FCH/DLFP methodneed not know the used SCH bitmap 412 a or the zone boosting factor(B_(z)) for decoding the FCH 410.

The preamble subcarriers (Y_(pa)) may be extracted from the output ofthe FFT component 320′ by paSCr extraction logic 702. The initial CElogic 704 may perform a channel estimation by dividing the preamblesubcarriers (Y_(pa)) by the known preamble (X_(m)=X_(pa)), for example,and a multiplier 706 may be used to effectively divide the result by theknown normal boosting factor for the preamble (B_(n) _(—) _(pascr)) inan effort to remove any boosting factors from the preamble, according tothe following:

$H_{e\_ pa} = {{\frac{Y_{pa}\left( {= {{HX}_{m}B_{n\_ pascr}}} \right)}{X_{m}} \times \frac{1}{B_{n\_ pascr}}} = H}$where H_(e) _(—) _(pa) is the initial estimate of the channel h based onthe preamble. Although multipliers are described with respect to FIGS.7-9, those skilled in the art may understand that any suitable logic forperforming the equivalent calculation (e.g., dividing by a value versusmultiplying by the multiplicative inverse of the value) may be used.

An interpolator 708 may perform frequency interpolation of the initialchannel estimate H_(e) _(—) _(pa) such that H_(e) _(—) _(pa)′ is theinterpolated channel estimate. In general for channel estimation,frequency interpolation, which is based on the initial channel estimate,may be used to estimate the frequency response of the subcarriers atfrequencies between those of the pilot subcarriers. For frequencyinterpolation, any suitable interpolation technique, such as linearinterpolation, may be used.

From the DL-PUSC zone at the output of the FFT component 320′, FCH pilotsubcarriers (Y_(fchp)) may be extracted by FCH pSCr extraction logic709, and FCH data subcarriers (Y_(fchd)) may be extracted by FCH dSCrextraction logic 710. Channel estimates (H_(e) _(—) _(pa,xp))corresponding to the FCH pilot subcarriers (i.e., frequency responses ofthe channel h at the same frequencies as the FCH pilot subcarriers) maybe extracted from the interpolated channel estimate (H_(e) _(—) _(pa)′)by corresponding pilot subcarrier extraction logic 712. Likewise,channel estimates (H_(e) _(—) _(pa,xd)) corresponding to the FCH datasubcarriers (i.e., frequency responses of the channel h at the samefrequencies as the FCH data subcarriers) may be extracted from theinterpolated channel estimate (H_(e) _(—) _(pa)′) by corresponding datasubcarrier extraction logic 714.

In the EQ combiner 603, the extracted FCH pilot subcarriers (Y_(fchp))may be divided by the extracted-corresponding-pilot preamble-derivedchannel estimate (H_(e) _(—) _(pa,xp)) and the known normal boostingfactor for the FCH pilots (B_(n) _(—) _(pscr)) in an effort to removethe effects of the channel h and any known boosting factors. If H_(e)_(—) _(pa,xp) is an accurate estimate of the channel h at the particularsubcarrier frequencies of interest, then H_(e) _(—) _(pa,xp) isapproximately equal to H, and the resulting equalized FCH pilot signal(R_(fchp)) is X_(m)B_(z) according to the following:

$R_{fchp} = {{\frac{Y_{fchp}\left( {= {{HX}_{m}B_{n\_ pscr}B_{z}}} \right)}{H_{{e\_ pa},{xp}}} \times \frac{1}{B_{n\_ pscr}}} = {X_{m}B_{z}}}$

Also in the EQ combiner 603, the extracted FCH data subcarriers(Y_(fchd)) may be divided by the extracted-corresponding-datapreamble-derived channel estimate (H_(e) _(—) _(pa,xd)) in an effort toremove the effects of the channel h. If H_(e) _(—) _(pa,xd) is anaccurate estimate of the channel h at the particular subcarrierfrequencies of interest, then H_(e) _(—) _(pa,xd) is approximately equalto H, and the resulting equalized FCH data signal (R_(fchd)) isX_(m)B_(z) according to the following:

$R_{fchd} = {\frac{Y_{fchd}\left( {= {{HX}_{m}B_{z}}} \right)}{H_{{e\_ pa},{xd}}} = {X_{m}B_{z}}}$Although a normal boosting factor is not typically applied to the FCHdata subcarriers, such a known normal boosting factor could be dividedout in a manner similar to the calculation for the equalized FCH pilotsignal. Also, keep in mind that the message X_(m) is different for theFCH pilots and data.

Once the equalized FCH pilot and data signals have been calculated, anormalization factor corresponding to zone boosting (B_(z) _(—) _(norm))may be calculated in any suitable manner. For example, the zone boostingnormalization factor may be calculated according to the following:B _(z) _(—) _(norm)=√{square root over (average_power(R _(fchp) ;R_(fchd)))}In the power normalizer 716, the equalized FCH pilot and data signalsmay be normalized according to the following:

$R_{fchp\_ norm} = \frac{R_{fchp}}{B_{z\_ norm}}$$R_{fchd\_ norm} = \frac{R_{fchd}}{B_{z\_ norm}}$which should be approximately equal to the corresponding FCH pilot anddata frequency-domain messages (X_(m)) in the transmitter 302.

Now that the wireless channel has been estimated and the boostingfactors have been effectively removed, demapping, CSI, LLR calculations,and decoding may proceed using the extracted-corresponding-datapreamble-derived channel estimate (H_(e) _(—) _(pa,xd)) and thenormalized FCH data signal (R_(fchd) _(—) _(norm)) to determine the DLFP412 from the accurately decoded FCH 410. For some embodiments, the CSIblock 516 may use the normalized FCH pilot signal (R_(fchp) _(—)_(norm)) instead of or in addition to the extracted-corresponding-datapreamble-derived channel estimate (H_(e) _(—) _(pa,xd)). Onedisadvantage of this method is the additional power normalizationperformed by the power normalizer 716 after equalization.

Exemplary Initial FCH Decoding Using FCH Pilots

FIG. 8 illustrates a block diagram 800 for another method of initialFCH/DLFP decoding, this one based on initial CE using the FCH pilots ofthe OFDM/A frame. Like the method of FIG. 7, the initial FCH/DLFP methodof FIG. 8 does not need to know the used SCH bitmap 412 a or the zoneboosting factor, and the interpolated estimate of the channel h (He_pa′)may be determined as described above.

From the DL-PUSC zone at the output of the FFT component 320′, FCH pilotsubcarriers may be extracted by FCH pSCr extraction logic 802. InitialCE logic 804 may perform channel estimation by dividing the extractedFCH pilot subcarriers (Y_(fchp)) by the known FCH pilots (X_(m)) fromthe transmitter 302. A multiplier 806 may be used to effectively dividethe result by the known normal boosting factor for the FCH pilots (B_(n)_(—) _(pscr)) in an effort to remove the normal boosting factor from theFCH pilot subcarriers (Y_(fchp)) according to the following:

$H_{e\_ fch} = {{\frac{Y_{fchp}\left( {= {{HX}_{m}B_{n\_ pscr}B_{z}}} \right)}{X_{m}} \times \frac{1}{B_{n\_ pscr}}} = {HB}_{z}}$where H_(e) _(—) _(fch) is the initial estimate of the channel h basedon the FCH pilots with zone boosting applied.

An interpolator 808 may perform frequency and time interpolation of theinitial channel estimate H_(e) _(—) _(fch) such that H_(e) _(—) _(fch)′is the interpolated channel estimate. In general for channel estimation,frequency interpolation may be used to estimate the frequency responseof the subcarriers at frequencies between those of the pilotsubcarriers, and time interpolation may be used to calculate thefrequency response of the subcarriers for OFDM symbols between OFDMsymbols composed of the pilot subcarriers. Any suitable interpolationtechnique, such as linear interpolation, may be used for the frequencyand/or time interpolation.

For time interpolation within the interpolator 808, if the first OFDMsymbol of the zone (i.e., the first FCH symbol) is being interpolated,then the interpolated preamble-based channel estimate (H_(e) _(—)_(pa)′) and the initial CE for the second symbol of the zone (i.e., thesecond FCH symbol) may be used to derive the time-interpolated channelestimate for the first symbol. For any other symbol of the zone, theinitial channel estimates for the symbols on either side of the currentsymbol (i.e., the (n−1)^(th) symbol and the (n+1)^(th) symbol) may beused to derive the time-interpolated channel estimate for the currentsymbol. Frequency interpolation may be performed using the resultingtime-interpolated channel estimate.

Also from the DL-PUSC zone at the output of the FFT component 320′, FCHdata subcarriers may be extracted by FCH dSCr extraction logic 812. Oncethe interpolated H_(e) _(—) _(fch)′ has been calculated, channelestimates (H_(e) _(—) _(fch,x)) corresponding to the FCH datasubcarriers (Y_(fchd)) may be extracted from the interpolated channelestimate (H_(e) _(—) _(fch)′) by corresponding data subcarrierextraction logic 810. The EQ combiner 603 may equalize the extracted FCHdata signals (Y_(fchd)) based on the extracted-corresponding-datachannel estimate (H_(e) _(—) _(fch,x)). If H_(e) _(—) _(fch,x) is anaccurate estimate of the channel h at the particular subcarrierfrequencies of interest, then the equalized FCH data signal (R_(fchp))should be approximately equal to the FCH data subcarriers (X_(m)) fromthe transmitter 302 according to the following equation:

$R_{fchd} = {\frac{Y_{fchd}\left( {= {{HX}_{m}B_{z}}} \right)}{H_{{e\_ fch},x}} = X_{m}}$

Because the FCH-pilot-derived channel estimates included the zoneboosting factor (B_(z)) and B_(z) has already been removed by the EQcombiner 603, power normalization need not occur in this particularinitial FCH/DLFP decoding scheme. Now that the wireless channel has beenestimated and the boosting factors have been effectively removed,demapping, CSI, LLR calculations, and decoding may proceed using theextracted-corresponding-data channel estimate (H_(e) _(—) _(fch,x)) andthe equalized FCH data signal (R_(fchd)) to accurately decode the FCH410 and hence, determine the DLFP 412.

Exemplary Initial FCH Decoding Using the Preamble and FCH Pilots

FIG. 9 illustrates a block diagram 900 for yet another method of initialFCH/DLFP decoding based on FCH pilots and on channel estimation (CE)using the preamble of an OFDM/A frame. Like the methods of FIGS. 7 and8, the initial FCH/DLFP method of FIG. 9 does not need to know the usedSCH bitmap 412 a. In the method of FIG. 9, the zone boosting factor(B_(z)) may be estimated using any suitable technique, such as trial anderror or a power measurement with a decision. The initial FCH decodingscheme associated with FIG. 9 may lead to a more accurate FCH than thescheme of FIG. 8, but the scheme of FIG. 9 is more complex and hasadditional calculation steps.

The interpolated estimate of the channel h (H_(e) _(—) _(pa)′) may bedetermined as described above with respect to FIG. 7. An initial channelestimate (H_(ie) _(—) _(fch)) based on the extracted FCH pilotsubcarriers (Y_(fchp)) may be determined in a manner similar to thedetermination of H_(e) _(—) _(fch) using the extraction logic 802, theinitial CE logic 804, and the multiplier 806 of FIG. 8 according to thefollowing:

$H_{ie\_ fch} = {{\frac{Y_{fchp}\left( {= {{HX}_{m}B_{n\_ pscr}B_{z}}} \right)}{X_{m}} \times \frac{1}{B_{n\_ pscr}}} = {HB}_{z}}$where H_(ie) _(—) _(fch) is the initial estimate of the channel h basedon the FCH pilots with zone boosting (B_(z)) applied. Channel estimates(H_(e) _(—) _(pa,x)) corresponding to the extracted FCH pilotsubcarriers (Y_(fchp)) may be extracted from the interpolated channelestimate (H_(e) _(—) _(pa)′) by corresponding pilot subcarrierextraction logic 902.

Average power calculation logic 904 may calculate the average power ofthe extracted-corresponding-pilot preamble-based channel estimate (H_(e)_(—) _(pa,x)), average power calculation logic 904′ may calculate theaverage power of the FCH-pilot-based channel estimate (H_(ie) _(—)_(fch)), and power ratio logic 906 may calculate the power ratio(P_(fch) _(—) _(pa)) between the FCH-pilot-based and theextracted-corresponding-pilot preamble-based channel estimates accordingto the following:

$P_{fch\_ pa} = {\frac{{mean}\left( {H_{ie\_ fch}}^{2} \right)}{{mean}\left( {H_{{e\_ pa},x}}^{2} \right)} = {B_{z}}^{2}}$

To estimate the zone boosting factor (B_(z)), the zone boostingestimator 908 may take the square root of the power ratio (P_(fch) _(—)_(pa)), and the result (B_(fch) _(—) _(pa)) may be compared against allpossible zone boosting factors to find the zone boosting factor nearestto B_(fch) _(—) _(pa). The nearest possible zone boosting factor may beselected as the estimated zone boosting factor (B_(ze)) according to thefollowing equations performed in the zone boosting estimator 908:B _(fch) _(—) _(pa)=√{square root over (P _(fch) _(—) _(pa))}=B _(z)B _(ze)=Nearest(B _(fch) _(—) _(pa),All Possible B _(z))For some embodiments, the estimated zone boosting factor may be setequal to the square root (B_(fch) _(—) _(pa)) of the power ratio.

A zone boosting inverter 910 may take the multiplicative inverse of theestimated zone boosting factor (B_(ze)). A multiplier 912 may multiplythe inverse (1/B_(ze)) with the FCH-pilot-based channel estimate (H_(ie)_(—) _(fch)) in an effort to normalize and remove the boosting factorfrom H_(ie) _(—) _(fch) according to the following:

$H_{{ie\_ fch}{\_ norm}} = {\frac{H_{ie\_ fch}}{B_{ze}} = H}$where H_(ie) _(—) _(fch) _(—) _(norm) is the normalized FCH-pilot-basedchannel estimate and should be approximately equal to the channeltransfer function H.

A second interpolator 914 may perform time and frequency interpolationusing either one or both of the channel estimates H_(e) _(—) _(pa,x) andH_(ie) _(—) _(fch) _(—) _(norm) according to the following:

$\begin{matrix}{H_{e\_ fch}^{''} = {{Interpolation}\left( \left\lfloor {H_{{e\_ pa},x};H_{{ie\_ fch}{\_ norm}}} \right\rfloor \right)}} \\{= H}\end{matrix}$The interpolated result (H_(e) _(—) _(fch)″) is designated as the singlechannel estimate for initial FCH decoding, which may be a more accuratechannel estimate closer to the actual wireless channel transfer functionH than either of the channel estimates H_(e) _(—) _(pa,x) and H_(ie)_(—) _(fch) _(—) _(norm). Any suitable interpolation technique, such aslinear interpolation, may be used for the time and/or frequencyinterpolation.

For example, to interpolate the first symbol of the FCH 410 (i.e.,symbol 1), the second interpolator 914 may use (a) the channel estimatefor the preamble, or symbol 0, (b) the initial channel estimate (i.e.,the channel estimate in the pilot position) for symbol 1, and (c) theinitial channel estimate for the second symbol of the FCH 410 (i.e.,symbol 2). Interpolation may be performed in time on (a), (b), and (c)to generate (b′), a time-interpolated first symbol of the FCH 410. Thetime-interpolated symbol 1 (b′) may then be frequency-interpolated toprovide frequency responses of the wireless channel corresponding tomissing subcarrier frequencies of interest.

Also from the DL-PUSC zone at the output of the FFT component 320′, FCHdata subcarriers may be extracted by FCH dSCr extraction logic 812. Oncethe interpolated H_(e) _(—) _(fch)″ has been calculated, a channelestimate (H_(e) _(—) _(fch,x)) corresponding to the FCH data subcarriers(Y_(fchd)) may be extracted from the interpolated channel estimate(H_(e) _(—) _(fch)″) by corresponding data subcarrier extraction logic915. The EQ combiner 603 may equalize the extracted FCH data signals(Y_(fchd)) based on the extracted-corresponding-data channel estimate(H_(e) _(—) _(fch,x))), and a multiplier 916 may effectively divide theresult by the estimated zone boosting factor (B_(ze)) in an effort toremove the zone boosting factor from the FCH data signal. If H_(e) _(—)_(fch,x) is an accurate estimate of the channel h at the particularsubcarrier frequencies of interest, then the equalized FCH data signal(R_(fchp)) should be approximately equal to the FCH data subcarriers(X_(m)) from the transmitter 302 according to the following equation:

$R_{fchd} = {{\frac{Y_{fchd}\left( {= {{HX}_{m}B_{z}}} \right)}{H_{{e\_ fch},x}} \times \frac{1}{B_{ze}}} = X_{m}}$

Because the zone boosting factor (B_(z)) has already been removed by themultiplier 916 (or the EQ combiner 603 for some embodiments), powernormalization need not occur in the initial FCH/DLFP decoding schemeassociated with FIG. 9. Now that the wireless channel has been estimatedand the boosting factors have been effectively removed, demapping, CSI,LLR calculations, and decoding may proceed using theextracted-corresponding-data channel estimate (H_(e) _(—) _(fch,x)) forinitial FCH decoding and the equalized FCH data signal (R_(fchd)) toaccurately decode the FCH 410 and hence, determine the DLFP 412.

For some embodiments, instead of estimating the zone boosting factoraccording to the power ratio (P_(fch) _(—) _(pa)), a trial-and-errorapproach using different zone boosting factors may be employed. Sinceall of the possible zone boosting factors (B_(z)) may be known, one ofthese may be selected for use as the estimated zone boosting factor(B_(ze)) in the equations above. Initial FCH/DLFP decoding may proceedas described above with respect to FIG. 9. The decoded FCH may bechecked, and if the decoded FCH is incorrect, the process may repeatwith a different possible zone boosting factor selected as the estimatedzone boosting factor (B_(ze)). If the decoded FCH is correct such thatthe DLFP 412 may be interpreted, the decoding of the OFDM/A frame mayproceed, starting with the decoding of the DL MAP 414. Thistrial-and-error approach may cause a latency issue in the initial FCHdecoding, however.

Exemplary Selection of Initial FCH Decoding

A device may be capable of performing any combination of one or moreinitial FCH/DLFP decoding methods presented above. Being based oninitial channel estimation (CE) using the preamble 408 of an OFDM/Aframe directly, the initial FCH/DLFP decoding method associated with theblock diagram 700 of FIG. 7 directly may offer fast FCH decoding.Associated with the block diagram 800 of FIG. 8, the initial FCH/DLFPdecoding method based on initial CE using the FCH pilots of the OFDM/Aframe may be used for simple FCH decoding without knowledge of the zoneboosting factor (B_(z)). The initial FCH/DLFP decoding method associatedwith the block diagram 900 of FIG. 9 and based on FCH pilots and onchannel estimation using the preamble of an OFDM/A frame may provide thebest performance by interpolating the channel in the preamble and thechannel in the next symbol of the FCH.

From the standpoint of decoding accuracy, the method of FIG. 9 may bethe best choice of the three methods, but the most complicated. Whenconsidering decoding speed, the method of FIG. 7 may be the best choice,although there may be some accuracy loss and an additional powernormalization block may be employed to cancel the zone boosting factor(B_(z)) in later stages. For ease of implementation, the method of FIG.8 may be the most suitable with no need to estimate the zone boostingfactor (B_(z)), although there may be some accuracy loss compared to themethod of FIG. 9.

Exemplary Overall Initial FCH Decoding

FIG. 10 illustrates a flow diagram of example operations 1000 forinitial FCH decoding based on the preamble of an OFDM/OFDMA frame. Theoperations may begin, at 1002, by determining an initial CE based on thepreamble of an OFDM/A frame received via a wireless channel. At 1004, aninterpolated CE based on the initial CE may be generated, for example,by estimating frequency responses of the wireless channel forsubcarriers not included in the initial CE (i.e., subcarriers that arenot preamble pilot subcarriers) as described above. Pilot and datasubcarriers may be extracted from the FCH at 1006, and from theinterpolated CE, channel estimates corresponding to both the FCH pilotand data subcarriers may be extracted at 1007.

At 1008, the extracted FCH pilot subcarriers may be divided by theextracted channel estimates corresponding to the FCH pilot subcarriersand a normal boosting factor in an effort to generate equalized FCHpilot subcarriers. At 1010, the extracted FCH data subcarriers may bedivided by the extracted channel estimates corresponding to the FCH datasubcarriers in an effort to generate equalized FCH data subcarriers. Anormalization factor corresponding to zone boosting may be determined at1012 based on the equalized FCH pilot subcarriers and the equalized FCHdata subcarriers. At 1014, the equalized FCH data subcarriers may bedivided by the zone boosting normalization factor in an effort tonormalize the equalized FCH data subcarriers, and the FCH may bedetermined based on the normalized FCH data subcarriers at 1016.

The operations 1000 of FIG. 10 described above may be performed byvarious hardware and/or software component(s) and/or module(s)corresponding to the means-plus-function blocks 1000A illustrated inFIG. 10A. In other words, blocks 1002 through 1016 illustrated in FIG.10 correspond to means-plus-function blocks 1002A through 1016Aillustrated in FIG. 10A.

FIG. 11 illustrates a flow diagram of example operations 1100 forinitial FCH decoding based on FCH pilots of an OFDM/OFDMA frame. Theoperations may begin, at 1102, by extracting pilot and data subcarriersfrom the FCH of a received OFDM/A signal. An initial CE based on theextracted FCH pilot subcarriers may be determined at 1104. At 1106, aninterpolated CE based on the initial CE may be generated, for example,by estimating frequency responses of the wireless channel for theextracted FCH data subcarriers as described above. Once the interpolatedCE has been generated, channel estimates corresponding to the FCH datasubcarriers may be extracted from it at 1107. The extracted FCH datasubcarriers may be divided at 1108 by the extracted channel estimatescorresponding to the FCH data subcarriers in an effort to form equalizedFCH data subcarriers, and the FCH may be determined based on theequalized FCH data subcarriers at 1110.

The operations 1100 of FIG. 11 described above may be performed byvarious hardware and/or software component(s) and/or module(s)corresponding to the means-plus-function blocks 1100A illustrated inFIG. 11A. In other words, blocks 1102 through 1110 illustrated in FIG.11 correspond to means-plus-function blocks 1102A through 1110Aillustrated in FIG. 11A.

FIG. 12 illustrates a flow diagram of example operations 1200 forinitial FCH decoding based on FCH pilots and on channel estimation usingthe preamble of an OFDM/OFDMA frame. The operations may begin, at 1202,by determining a first initial CE based on the preamble of an OFDM/Aframe received via a wireless channel. At 1204, a first interpolated CEbased on the first initial CE may be generated, for example, byestimating frequency responses of the wireless channel for subcarriersnot included in the first initial CE (i.e., subcarriers that are notpreamble pilot subcarriers) as described above.

Pilot and data subcarriers may be extracted from the FCH at 1206, andfrom the first interpolated CE, channel estimates corresponding to theFCH pilot subcarriers may be extracted at 1208. At 1210, a secondinitial CE based on the extracted FCH pilot subcarriers may bedetermined. A zone boosting factor may be estimated at 1212, and at1214, the second initial CE may be normalized by the estimated zoneboosting factor.

At 1216, a second interpolated CE based on the extracted channelestimates corresponding to the FCH pilot subcarriers and on thenormalized second initial CE may be generated, for example, as describedabove with respect to the interpolator 914. Once the second interpolatedCE has been generated, channel estimates corresponding to the FCH datasubcarriers may be extracted from it at 1217. The extracted FCH datasubcarriers from 1206 may be divided at 1218 by the extracted channelestimates corresponding to the FCH data subcarriers and the estimatedzone boosting factor in an effort to form equalized FCH datasubcarriers. The FCH may be determined based on the equalized FCH datasubcarriers at 1220.

The operations 1200 of FIG. 12 described above may be performed byvarious hardware and/or software component(s) and/or module(s)corresponding to the means-plus-function blocks 1200A illustrated inFIG. 12A. In other words, blocks 1202 through 1220 illustrated in FIG.12 correspond to means-plus-function blocks 1202A through 1220Aillustrated in FIG. 12A.

As used herein, the term “determining” encompasses a wide variety ofactions. For example, “determining” may include calculating, computing,processing, deriving, investigating, looking up (e.g., looking up in atable, a database or another data structure), ascertaining and the like.Also, “determining” may include receiving (e.g., receiving information),accessing (e.g., accessing data in a memory) and the like. Also,“determining” may include resolving, selecting, choosing, establishingand the like.

Information and signals may be represented using any of a variety ofdifferent technologies and techniques. For example, data, instructions,commands, information, signals and the like that may be referencedthroughout the above description may be represented by voltages,currents, electromagnetic waves, magnetic fields or particles, opticalfields or particles or any combination thereof.

The various illustrative logical blocks, modules and circuits describedin connection with the present disclosure may be implemented orperformed with a general purpose processor, a digital signal processor(DSP), an application specific integrated circuit (ASIC), a fieldprogrammable gate array signal (FPGA) or other programmable logic device(PLD), discrete gate or transistor logic, discrete hardware componentsor any combination thereof designed to perform the functions describedherein. A general purpose processor may be a microprocessor, but in thealternative, the processor may be any commercially available processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration.

The steps of a method or algorithm described in connection with thepresent disclosure may be embodied directly in hardware, in a softwaremodule executed by a processor, or in a combination of the two. Asoftware module may reside in any form of storage medium that is knownin the art. Some examples of storage media that may be used includerandom access memory (RAM), read only memory (ROM), flash memory, EPROMmemory, EEPROM memory, registers, a hard disk, a removable disk, aCD-ROM and so forth. A software module may comprise a singleinstruction, or many instructions, and may be distributed over severaldifferent code segments, among different programs, and across multiplestorage media. A storage medium may be coupled to a processor such thatthe processor can read information from, and write information to, thestorage medium. In the alternative, the storage medium may be integralto the processor.

The methods disclosed herein comprise one or more steps or actions forachieving the described method. The method steps and/or actions may beinterchanged with one another without departing from the scope of theclaims. In other words, unless a specific order of steps or actions isspecified, the order and/or use of specific steps and/or actions may bemodified without departing from the scope of the claims.

The functions described may be implemented in hardware, software,firmware, or any combination thereof If implemented in software, thefunctions may be stored as one or more instructions or sets ofinstructions on a computer-readable medium or storage medium. A storagemedia may be any available media that can be accessed by a computer, orone or more instruction processing devices. By way of example, and notlimitation, such computer-readable media can comprise RAM, ROM, EEPROM,CD-ROM or other optical disk storage, magnetic disk storage or othermagnetic storage devices, or any other medium that can be used to carryor store desired program code in the form of instructions or datastructures and that can be accessed by a computer. Disk and disc, asused herein, include compact disc (CD), laser disc, optical disc,digital versatile disc (DVD), High Definition DVD (HD DVD®), floppydisk, and Blu-ray® disc where disks usually reproduce data magnetically,while discs reproduce data optically with lasers.

Software or instructions may also be transmitted over a transmissionmedium. For example, if the software is transmitted from a website,server, or other remote source using a coaxial cable, fiber optic cable,twisted pair, digital subscriber line (DSL), or wireless technologiessuch as infrared, radio, and microwave, then the coaxial cable, fiberoptic cable, twisted pair, DSL, or wireless technologies such asinfrared, radio, and microwave are included in the definition oftransmission medium.

Further, it should be appreciated that modules and/or other appropriatemeans for performing the methods and techniques described herein can bedownloaded and/or otherwise obtained by a user terminal and/or basestation as applicable. For example, such a device can be coupled to aserver to facilitate the transfer of means for performing the methodsdescribed herein. Alternatively, various methods described herein can beprovided via storage means (e.g., RAM, ROM, a physical storage mediumsuch as a compact disc (CD) or floppy disk, etc.), such that a userterminal and/or base station can obtain the various methods uponcoupling or providing the storage means to the device. Moreover, anyother suitable technique for providing the methods and techniquesdescribed herein to a device can be utilized.

It is to be understood that the claims are not limited to the preciseconfiguration and components illustrated above. Various modifications,changes and variations may be made in the arrangement, operation anddetails of the methods and apparatus described above without departingfrom the scope of the claims.

What is claimed is:
 1. A method comprising: extracting pilot and datasubcarriers from a frame control header (FCH) of a signal received via awireless channel; determining an initial channel estimate (CE) based onthe extracted FCH pilot subcarriers by dividing the extracted FCH pilotsubcarriers of the received signal by known FCH pilot subcarriers and anormal boosting factor corresponding to the FCH pilot subcarriers,wherein the initial CE is approximately equal to a frequency response ofthe wireless channel multiplied with a zone boosting factor of a PUSC(partial usage of subchannels) zone; generating an interpolated CE basedon the initial CE by estimating frequency responses of the channel forthe extracted FCH data subcarriers; from the interpolated CE, extractinga channel estimate corresponding to the FCH data subcarriers; dividingthe extracted FCH data subcarriers by the extracted channel estimate toform equalized FCH data subcarriers; and determining the FCH based onthe equalized FCH data subcarriers.
 2. The method of claim 1, whereingenerating the interpolated CE involves linear interpolation betweenelements of the initial CE associated with the extracted FCH pilotsubcarriers in at least one of time and frequency.
 3. A non-transitorycomputer-readable medium containing a program for initially decoding aframe control header (FCH), which, when executed by a processor,performs operations comprising: extracting pilot and data subcarriersfrom the FCH of a signal received via a wireless channel; determining aninitial channel estimate (CE) based on the extracted FCH pilotsubcarriers by dividing the extracted FCH pilot subcarriers of thereceived signal by known FCH pilot subcarriers and a normal boostingfactor corresponding to the FCH pilot subcarriers, wherein the initialCE is approximately equal to a frequency response of the wirelesschannel multiplied with a zone boosting factor of a PUSC (partial usageof subchannels) zone; generating an interpolated CE based on the initialCE by estimating frequency responses of the channel for the extractedFCH data subcarriers; from the interpolated CE, extracting a channelestimate corresponding to the FCH data subcarriers; dividing theextracted FCH data subcarriers by the extracted channel estimate to formequalized FCH data subcarriers; and determining the FCH based on theequalized FCH data subcarriers.
 4. An apparatus for wirelesscommunication, comprising: means for extracting pilot and datasubcarriers from a frame control header (FCH) of a signal received via awireless channel; means for determining an initial channel estimate (CE)based on the extracted FCH pilot subcarriers by dividing the extractedFCH pilot subcarriers of the received signal by known FCH pilotsubcarriers and a normal boosting factor corresponding to the FCH pilotsubcarriers, wherein the initial CE is approximately equal to afrequency response of the wireless channel multiplied with a zoneboosting factor of a PUSC (partial usage of subchannels) zone; means forgenerating an interpolated CE based on the initial CE by estimatingfrequency responses of the channel for the extracted FCH datasubcarriers; means for extracting, from the interpolated CE, a channelestimate corresponding to the FCH data subcarriers; means for dividingthe extracted FCH data subcarriers by the extracted channel estimate toform equalized FCH data subcarriers; and means for determining the FCHbased on the equalized FCH data subcarriers.
 5. A receiver for wirelesscommunication, comprising: subcarrier extraction logic configured toextract pilot and data subcarriers from a frame control header (FCH) ofa signal received via a wireless channel; initial channel estimationlogic configured to determine an initial channel estimate (CE) based onthe extracted FCH pilot subcarriers by dividing the extracted FCH pilotsubcarriers of the received signal by known FCH pilot subcarriers and anormal boosting factor corresponding to the FCH pilot subcarriers,wherein the initial CE is approximately equal to a frequency response ofthe wireless channel multiplied with a zone boosting factor of a PUSC(partial usage of subchannels) zone; interpolation logic configured togenerate an interpolated CE based on the initial CE by estimatingfrequency responses of the channel for the extracted FCH datasubcarriers; CE extraction logic configured to extract, from theinterpolated CE, a channel estimate corresponding to the FCH datasubcarriers; division logic configured to divide the extracted FCH datasubcarriers by the extracted channel estimate to form equalized FCH datasubcarriers; and interpretation logic configured to determine the FCHbased on the equalized FCH data subcarriers.
 6. The receiver of claim 5,wherein the interpretation logic comprises at least one of channel stateinformation (CSI) logic, log likelihood ratio (LLR) logic, and channeldecoding logic configured to decode the FCH.
 7. A mobile device,comprising: a receiver front end for receiving a signal transmitted viaa wireless channel; subcarrier extraction logic configured to extractpilot and data subcarriers from a frame control header (FCH) of thereceived signal; initial channel estimation logic configured todetermine an initial channel estimate (CE) based on the extracted FCHpilot subcarriers by dividing the extracted FCH pilot subcarriers of thereceived signal by known FCH pilot subcarriers and a normal boostingfactor corresponding to the FCH pilot subcarriers, wherein the initialCE is approximately equal to a frequency response of the wirelesschannel multiplied with a zone boosting factor of a PUSC (partial usageof subchannels) zone; interpolation logic configured to generate aninterpolated CE based on the initial CE by estimating frequencyresponses of the channel for the extracted FCH data subcarriers; CEextraction logic configured to extract, from the interpolated CE, achannel estimate corresponding to the FCH data subcarriers; divisionlogic configured to divide the extracted FCH data subcarriers by theextracted channel estimate to form equalized FCH data subcarriers; andinterpretation logic configured to determine the FCH based on theequalized FCH data subcarriers.
 8. A method comprising: extracting pilotand data subcarriers from a frame control header (FCH) of a signalreceived via a wireless channel; determining an initial channel estimate(CE) based on the extracted FCH pilot subcarriers; generating aninterpolated CE based on the initial CE by estimating frequencyresponses of the channel for the extracted FCH data subcarriers; fromthe interpolated CE, extracting a channel estimate corresponding to theFCH data subcarriers; dividing the extracted FCH data subcarriers by theextracted channel estimate to form equalized FCH data subcarriers;determining the FCH based on the equalized FCH data subcarriers;extracting a zone boosting factor of a PUSC (partial usage ofsubchannels) zone from the determined FCH; and decoding the FCH again ordecoding another FCH of another signal received via the wirelesschannel, based on the extracted zone boosting factor.
 9. Anon-transitory computer-readable medium containing a program forinitially decoding a frame control header (FCH), which, when executed bya processor, performs operations comprising: extracting pilot and datasubcarriers from the FCH of a signal received via a wireless channel;determining an initial channel estimate (CE) based on the extracted FCHpilot subcarriers; generating an interpolated CE based on the initial CEby estimating frequency responses of the channel for the extracted FCHdata subcarriers; from the interpolated CE, extracting a channelestimate corresponding to the FCH data subcarriers; dividing theextracted FCH data subcarriers by the extracted channel estimate to formequalized FCH data subcarriers; determining the FCH based on theequalized FCH data subcarriers; extracting a zone boosting factor of aPUSC (partial usage of subchannels) zone from the determined FCH; anddecoding the FCH again or decoding another FCH of another signalreceived via the wireless channel, based on the extracted zone boostingfactor.
 10. An apparatus for wireless communication, comprising: meansfor extracting pilot and data subcarriers from a frame control header(FCH) of a signal received via a wireless channel; means for determiningan initial channel estimate (CE) based on the extracted FCH pilotsubcarriers; means for generating an interpolated CE based on theinitial CE by estimating frequency responses of the channel for theextracted FCH data subcarriers; means for extracting, from theinterpolated CE, a channel estimate corresponding to the FCH datasubcarriers; means for dividing the extracted FCH data subcarriers bythe extracted channel estimate to form equalized FCH data subcarriers;means for determining the FCH based on the equalized FCH datasubcarriers; means for extracting a zone boosting factor of a PUSC(partial usage of subchannels) zone from the determined FCH; and meansfor decoding the FCH again or means for decoding another FCH of anothersignal received via the wireless channel, based on the extracted zoneboosting factor.
 11. A receiver for wireless communication, comprising:subcarrier extraction logic configured to extract pilot and datasubcarriers from a frame control header (FCH) of a signal received via awireless channel; initial channel estimation logic configured todetermine an initial channel estimate (CE) based on the extracted FCHpilot subcarriers; interpolation logic configured to generate aninterpolated CE based on the initial CE by estimating frequencyresponses of the channel for the extracted FCH data subcarriers; CEextraction logic configured to extract, from the interpolated CE, achannel estimate corresponding to the FCH data subcarriers; divisionlogic configured to divide the extracted FCH data subcarriers by theextracted channel estimate to form equalized FCH data subcarriers;interpretation logic configured to determine the FCH based on theequalized FCH data subcarriers; zone boosting factor extraction logicconfigured to extract a zone boosting factor of a PUSC (partial usage ofsubchannels) zone from the determined FCH; and decoding logic configuredto decode the FCH again or to decode another FCH of another signalreceived via the wireless channel, based on the extracted zone boostingfactor.